U.S. Defense Secretary Donald Rumsfeld has ended his 48-hour visit to China, expressing concern about an expansion of the country's missile capability. He also re-stated his suspicions about Beijing's official defense budget, even though China's minister of defense tried to ease that concern.

At the Chinese Military Academy Thursday, Secretary Rumsfeld told a gathering of senior officers that China should provide more information about its defense program, and he added a new item to the list of elements of that program that worry him.

"China, of course, is expanding its missile forces and enabling those forces to reach many areas of the world, well beyond the Pacific region," he said. "Those advances in China's strategic strike capability raise questions, particularly when there is an imperfect understanding about such developments on the part of others."

Secretary Rumsfeld expressed that concern the day after he became the first foreign official to visit the new headquarters of China's strategic missile command. There, a senior official sought to reassure him that China would not be the first to use nuclear weapons in any conflict.

The issue was the latest of several concerns Mr. Rumsfeld raised in meetings with Chinese officials. He repeatedly mentioned what he calls China's preference for regional organizations that exclude the United States, its refusal to allow the United States to observe its military exercises with other countries and its effort to convince Central Asian nations to expel U.S. forces that support operations in Afghanistan.

He also stressed discrepancies about China's defense spending. On Wednesday, Defense Minister Cao Gangchuan tried to ease Mr. Rumsfeld's concerns, saying China reports all of its military spending. Later that day, U.S. officials indicated part of the discrepancy appears to be different accounting methods. But Secretary Rumsfeld mentioned the issue again Thursday at the military academy, which is a strategic research institute attached to China's powerful Central Military Commission.

"Under our law, the Department of Defense is required to issue a report about your military capabilities every year. It's prepared by experts from all kinds of information, including open source information, and consultation with experts around the world," explained Mr. Rumsfeld. "And as you may have read, it suggests the actual expenditures by your country are something like two or three times what the published figures suggest."

Asked about the secretary's decision to raise the budget issue again, his chief spokesman, Lawrence DiRita, said there is a benefit to repetition. Asked whether Secretary Rumsfeld was satisfied with what he heard in Beijing, Mr. DiRita said the secretary did not expect definitive conclusions to any issues, but rather wanted to express his concerns and gain a better understanding of Chinese thinking on the issues, and he accomplished those goals.

Secretary Rumsfeld had said he wanted more "transparency" on China's military programs, and Mr. DiRita said he achieved some of that on a personal level with Defense Minister Cao.

Mr. DiRita also reported that during a closed session Thursday, Secretary Rumsfeld stressed that military exchanges and other types of cooperation can be increased even as the two governments work through their differences. Mr. Rumsfeld and Mr. Cao promised to take a personal interest in increasing U.S.-China military contacts.

The tone of the visit alternated between statements about common goals and expressions of a desire to work together, and less harmonious moments when Mr. Rumsfeld expressed his concerns and Chinese officials defended their policies and challenged his views.

Both sides used words like "candid" and "frank" to describe the talks, indicating it was, as U.S. officials had predicted, a "non-euphoric" encounter. But as Secretary Rumsfeld flew out of Beijing, his spokesman, Mr. DiRita, called the visit time "extremely well spent."